The present disclosure relates to a technical field of semiconductor, and particularly relates to a semiconductor device and a method for manufacturing the same.
The third-generation semiconductor material gallium nitride (GaN) has a dielectric breakdown electric field much higher than that of the first-generation semiconductor silicon (Si) or the second-generation semiconductor gallium arsenide (GaAs), and the value thereof is as high as 3 MV/cm, so that the electronic device of the material can withstand a high electric field strength. At the same time, gallium nitride (GaN) can form a heterojunction structure with other gallium-based compound semiconductors (e.g., Group III nitride semiconductors). As Group III nitride semiconductors have strong spontaneous polarization and piezoelectric polarization effects, they can form Two Dimensional Electron Gas (2DEG) channels with high electron concentration near the interface of the heterojunction, and such a heterojunction structure can also effectively reduce scattering of ionized impurities, so the electron mobility in the channel is significantly increased. The gallium nitride high electron mobility transistor formed on the basis of such a heterojunction structure can conduct a high current at a high frequency and has a very low on-resistance. The above characteristics make the gallium nitride high electron mobility transistor suitable for manufacturing high frequency high power radio frequency devices and switching devices with high withstand voltage and high current.
In the manufacturing process of a gallium nitride high electron mobility transistor, gate of the gallium nitride high electron mobility transistor is a Schottky metal-semiconductor contact with rectifying characteristics, and the metals used, such as nickel (Ni), platinum (Pt), and gold (Au), are required having higher work function. Because nickel (Ni) has good adhesion to semiconductor material, it can ensure that the gate metal does not fall off during a stripping process, and nickel (Ni) is generally used as the underlying metal of the gate in contact with the semiconductor material. When the device is operating, the gate and the drain are subjected to a high voltage, and there is an electric field peak at the edge region of the gate close to the drain, which causes an increase in gate current of the device, and thus results in reduced reliability. In the T-type gate manufacturing process, silicon nitride (SiN) is generally used as a blocking layer. In the above device manufacturing method, the Schottky metal-semiconductor contact edge is in contact with the silicon nitride blocking layer to form nickel silicide (NiSi) with a lower work function, and a Schottky contact with high reverse leakage characteristics is formed in the region where the nickel silicide (NiSi) is in contact with the semiconductor material. During operation at high voltage, the location where nickel silicide (NiSi) is generated is changed into a leakage path due to the high electric field, which causes the gate leakage to increase, and thus causes a reliability problem.
The existing method for suppressing a high electron mobility transistor device from forming nickel silicide (NiSi) is to form nickel oxide (NiO) on the edge of nickel (Ni), and it avoids contact between nickel (Ni) and silicon nitride (SiN) by using nickel oxide (NiO), thereby avoiding formation of nickel silicide (NiSi). Although this method can reduce gate leakage of the device, the nickel oxide (NiO) manufacturing process may increase the current collapse of the device, and additional processes are further required to suppress current collapse [see Chinese patent application No. 201410486993.8 and Chinese patent application No. 201010226347.X], which increases the process complexity.